Imaging block and imaging apparatus

ABSTRACT

An imaging block includes a prism, first and second imaging devices, an analog/digital convertor, a timing generator, and first, second, third circuit boards. The prism separates light incident through a lens into at least two colors and outputs the light. The first and second imaging devices are each generates a video signal by photoelectrically converting the light. The analog/digital converter converts the video signal output from each of the devices into a digital signal. The timing generator generates a video-signal processing clock for driving the first imaging device, the second imaging device, and the analog/digital converter. The first imaging device is mounted on the first circuit board. The analog/digital converter and the timing generator are mounted on the second circuit board. The second imaging device is mounted on third circuit board and connected to both the first circuit board and the second circuit board through a cable.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2007-070958 filed in the Japanese Patent Office on Mar.19, 2007, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an imaging block suitably applicable to anendoscope or the like and to an imaging apparatus including such animaging block.

2. Description of the Related Art

For obtaining high-definition pictures with imaging apparatuses usingimaging devices such as CCDs (Charge Coupled Devices) and CMOSs(Complementary Metal Oxide Semiconductors), it is important tofaithfully transmit video signals obtained with the imaging devices asfar as possible with respect to phases, frequencies, and so on.

However, in recent years, a high-definition and small-sized imagingapparatus has been desired, and therefore a high clock frequency is usedin a system of signal processing circuit. Thus, phase differences,deterioration of frequency characteristics and so on may largely affectthe quality of signals. Accordingly, various procedures have beendevised for preventing such phase differences and deterioration offrequency characteristics.

Japanese Unexamined Patent Application Publication No. H07-313453discloses an endoscope including an imaging device in which signaltransmission is carried out using a flexible print board with anoise-shielding performance.

SUMMARY OF THE INVENTION

For example, if an imaging device and an analog/digital converter(hereinafter, referred to as A/D converter) for converting a videosignal obtained with the imaging device into a digital signal arearranged apart from each other, an analog signal is transmitted a longdistance. In such case, signals output from another neighboring circuitmay become noise and have a high probability of coupling into analogsignals.

In the case where the transmission path of an analog signal is long, thephase and frequency characteristics of the signal may be oftendeteriorated during the signal transmission, causing resolution to bedeteriorated. In particular, when CCD is used as an imaging device and a3-chip imaging system is employed, the electrical fixing precision ofthree CCDs may decrease due to deterioration in the phase and frequencycharacteristics of the analog signal.

In addition, the area of a circuit board may be reduced to satisfy therequest for obtaining a small-sized imaging apparatus. However, in thecase of arranging another circuit, such as an A/D converter, on thecircuit board where the imaging device is mounted, the circuit board mayneed to be large.

It is desirable to provide an imaging block and an imaging apparatuswhich are small-sized and capable of preventing video signals fromdeteriorating.

According to an embodiment of the invention, there is provided animaging block and according to another embodiment of the invention,there is provided an imaging apparatus. The imaging block and imagingapparatus each include a prism, a first imaging device, a second imagingdevice, an analog/digital converter, and a timing generator. The prismis configured to separate light incident through a lens into at leasttwo colors and output the light. The first imaging device and the secondimaging device are configured to generate video signals byphotoelectrically converting the separated light output from the prism,respectively. The analog/digital converter is configured to convert thevideo signals output from the first and second imaging devices intodigital signals. The timing generator is configured to generate avideo-signal processing clock for driving the imaging devices and theanalog/digital converter. The imaging block and imaging apparatus eachfurther include a first circuit board on which the first imaging deviceis mounted, a second circuit board on which the analog/digital converterand the timing generator are mounted, and a third circuit board, onwhich the second imaging device is mounted, electrically connected toboth the first and second circuit boards. Furthermore, the secondcircuit board is arranged such that a surface thereof can besubstantially perpendicular to a surface of the first circuit board anda surface of the third circuit board. In addition, the analog/digitalconverter and the timing generator are mounted on another surface of thesecond circuit board, which is opposite to the surface on the side whereboth the first and third circuit boards are arranged.

Accordingly, both the analog/digital converter and the timing generatorare allowed to be arranged on the second circuit board. Here, the secondcircuit board is arranged substantially perpendicular to the firstcircuit board and the third circuit board, on which the respectiveimaging devices are mounted. Thus, the analog/digital converter and thetiming generator are arranged on the rear of the side where the firstcircuit board and the second circuit board are arranged.

According to the above embodiments of the invention, the analog/digitalconverter is not arranged on any of the first circuit board and thethird circuit board, which are fixed to the prism, so that the area ofthe circuit board can be restricted. In addition, the timing generatorand the imaging device are arranged on the sides opposite to each other,so that signals from the timing generator can be prevented from couplinginto video signals obtained from the imaging devices as noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an exemplified internalconfiguration of an imaging apparatus according to an embodiment of theinvention.

FIG. 2 is a perspective view illustrating an exemplified configurationof an imaging block according to an embodiment of the invention.

FIGS. 3A and 3B are diagrams illustrating an exemplified configurationof an imaging block according to an embodiment of the invention, whereFIG. 3A is a perspective view of the imaging block and FIG. 3B isanother perspective view thereof, which are viewed from differentangles.

FIGS. 4A and 4B are diagrams illustrating an exemplified arrangement ofcircuit boards according to an embodiment of the invention, where FIG.4A is a perspective view of the circuit board in an extended state andFIG. 4B is a perspective view of the circuit board in a folded state.

FIGS. 5A and 5B are diagrams illustrating an exemplified arrangement ofcircuit boards according to another embodiment of the invention.

FIG. 6 is an exploded perspective view illustrating an exemplifiedconfiguration of each layer of the circuit boards according to anembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the invention will be described withreference to the attached drawings.

FIG. 1 illustrates an exemplified configuration of an imaging apparatusaccording to an embodiment of the invention. An imaging apparatus 100 ofthe embodiment is applicable to imaging apparatuses used in variousapplications, such as a medical endoscope. The imaging apparatus 100illustrated in FIG. 1 employs a 3-chip imaging system and includes threeCCD imaging devices (hereinafter, simply referred to as imaging devices)11G, 11R, 11B. The respective CCDs 11G, 11R, 11B generate electricsignals by photoelectrically converting respective light beams G(green), R (red), and B (blue) separated with a color-separation prism(not shown) from light passing through a lens (not shown). Furthermore,the imaging apparatus 100 includes a vertical transfer driver(hereinafter, referred to as a V driver) 20 and a horizontal transferdrivers (hereinafter, referred to as H drivers) 14G, 14R, 14B. The Vdriver 20 vertically transfers signal electric charges photoelectricallyconverted and accumulated in the respective CCDs 11G, 11R, 11B. The Hdrivers 14G, 14R, 14B horizontally transfer signal electric chargesvertically transferred from the V driver 20.

The V driver 20 supplies vertical transfer pulses Vφ1 to Vφ4 to the CCDs11G, 11R, 11B, respectively. The H drivers 14G, 14R, 14B supplyhorizontal transfer pulses H1 and H2 to the CCDs 11G, 11R, 11B,respectively. In addition, the H drivers 14G, 14R, 14B supply resetpulses RG to reset the signal charges accumulated in the CCDs 11G, 11R,11B, respectively. These pulses applied to the CCDs 11G, 11R, 11B aregenerated in synchronization with video sync clock (CAM_CLK) suppliedfrom a timing generator 19.

Upon receiving reference clock (HCLK) supplied from a first control unit17 for controlling respective units in the imaging apparatus 100, thetiming generator 19 generates video sync clock (CAM_CLK) for driving theCCDs 11G, 11R, 11B, the V driver 20, the H drivers 14G, 14R, 14B, andlater-described CDS circuits 13G, 13R, 13G and analog/digital converters(A/D converters) 15G, 15R, 15B and then supplies the video sync clock(CAM_CLK) to them, respectively. The video sync clock has a frequencyfor video-signal processing in synchronization with the horizontalfrequency and the vertical frequency of the video signal.

Signal charges obtained from CCDs 11G, 11R, 11B are read by theabove-described V driver 20 and H drivers 14G, 14R, 14B and thenconverted to voltages corresponding to the signal charges at an outputcircuit (not shown), followed by being supplied to CDS (CorrelatedDouble Sampling) circuits 13G, 13R, 13B, respectively.

The CDS circuits 13G, 13R, 13B carry out sampling of respective outputsignals obtained from the CCDs 11G, 11R, 11B to reduce reset noisesincluded in the signals. The video signals output from the CDS circuits13G, 13R, 13B are supplied to the A/D converters 15G, 15R, 15B afterbeing adjusted to constant signal levels in an AGC (Automatic GainControl) circuit (not shown). The A/D converters 15G, 15R, 15B convertvideo signals (analog signals) into digital signals, respectively.

A block (hereinafter, referred to as a camera block 50) on which theabove-described optical system, CCDs 11G, 11R, 11B, CDSs 13G, 13R, 13B,and other circuits are mounted is provided on a circuit board separatedand distant from a board on which a video-processing unit 16 carryingout image-processing of video signals output from the block is provided.The camera block 50 is connected to the block, on which thevideo-processing unit 16 is mounted, through a cable 1 connecting aconnector 2 a on the side of the camera block 50 and a connector 2 b onthe side of the video-processing unit 16. The video-processing unit 16carries out feed-back clamp processing of fixing a black level OB(optical black) at a predetermined standard value, knee correction forcompressing a signal of a certain level or more, gamma correction forcarrying out correction according to a gamma curve where the level ofthe video signal is defined, white-dip processing for correcting whitebalance, and so on.

The connector 2 a of the camera block 50 is also connected to the firstcontrol unit 17 that controls each unit of the imaging apparatus 100.The first control unit 17 includes a micro computer or the like. In thisembodiment, for reducing the amount of signals transmitted from thefirst control unit 17 to the respective units in the camera block 50, asecond control unit 18 is installed in the camera block 50. The secondcontrol unit 18 translates a setup instruction command to each unit inthe camera block 50 among commands transmitted from the first controlunit 17 and transmits such command to each unit.

The second control unit 18 carries out, for example, control of changingshutter speed for the timing generator 19, gain control and switchinginstruction of video rates (such as 50i/60i) for the A/D converters 15G,15R, 15B. In addition, for lowering the power consumption of the imagingapparatus 100, the second control unit 18 may control the respectiveunits in the camera block 50 to independently switch to a standby modeor control the settings of respective units to be periodicallyinitialized.

Subsequently, referring to FIG. 2, an exemplified configuration of animaging block 200 including a color separation prism 30, the imagingdevices 11G, 11R, 11B, and so on will be described. FIG. 2 is aperspective view showing the light incident side of the image block 200.The imaging block 200 is connected to a lens block 2 represented by thebroken line in FIG. 2 through a lens-mounting base 10. As shown in thefigure, a positioning hole 10 a is formed in the lens-mounting base 10.The lens block 2 and the imaging block 200 can be fixed together withhigh dimensional accuracy using a screw inserted in the hole 10 a.

The lens-mounting base 10 is provided with a window 31 on which subjectlight passing through a lens 2 a of the lens block 2 is incident. Thecolor separation prism 30 is fixed to the rear of the lens-mounting base10 in the forward direction of the subject light. The prism 30 separatesthe subject light incident from the window 31 into three color lightbeams, R, G, and B.

The color separation prism 30 includes a block for transmitting the Blight beam, a block for transmitting the R light beam, and a block fortransmitting the G light beam. The imaging device 11B forphotoelectrically converting the B light beam, the imaging device 11Gfor photoelectrically converting the G light beam, and the imagingdevice 11R for photoelectrically converting the R light beam are fixedto three output surfaces of the respective blocks from which therespective rays of light separated into R, G, and B are output. Theimaging device 11B alone is illustrated in FIG. 2. The imaging devices11R and 11G are not illustrated in the figure.

As shown in FIG. 2, a circuit board 40A (second circuit board) isarranged at the position substantially perpendicular to circuit boards40B, 40G, 40R, respectively. In addition, a power-decoupling capacitor60 is arranged on the circuit board 40A. Furthermore, the A/D converters15R, 15G, 15B, second control unit 18, timing generator 19, and so onare arranged on the rear surface of the circuit board 40A. Thearrangement of the respective units on the rear surface of the circuitboard 40A will be described later in detail.

FIGS. 3A and 3B are diagrams illustrating an exemplified configurationof the imaging block 200 when the window 31 faces downward. FIG. 3A is aperspective view showing the surface of the circuit board 40A facingforward on which the decoupling capacitor 60 is arranged and FIG. 3B isa perspective view of the rear surface of the circuit board 40A.

The imaging devices 11B, 11G, 11R fixed on three respective outputsurfaces of the color separation prism 30 are connected to the circuitboard 40B (first circuit board), the circuit board 40G (third circuitboard), and the circuit board 40R (first circuit board), respectively.The respective imaging devices are connected to the circuit boards bysoldering the terminals of the imaging devices to the rear surfaces ofthe respective circuit boards 40B, 40G, 40R.

The CDS circuits 13B, 13G, 13R are arranged on the other surfaces of therespective circuit boards 40B, 40G, 40R, on which the imaging devices11B, 11G, 11R are not connected. In addition, the respective circuitboards 40 are electrically connected to one another through a flexiblecable 41 that is a circuit board with flexibility.

Ground boards 70B, 70G, 70R are also connected to the flexible cable 41,respectively. In addition, the ground boards 70B, 70G, 70R are contactedwith a conductive plate 90 made of a copper foil or the like. The groundboards 70B, 70G, 70R are fixed to the conductive plate 90 using screws80B, 80G, 80R, respectively.

Next, referring to FIG. 3B, the arrangement of the respective units onthe rear surface of the circuit board 40A will be described. As shown inFIG. 3B, the timing generator 19, the second control unit 18, the A/Dconverters 15R, 15G, 15B are arranged on the circuit board 40A in theorder from the upper left. The A/D converters 15R, 15G, 15B arecontacted with a hear sink 45 to deal with radiated heat. The A/Dconverters 15R, 15G, 15B are arranged in the vicinity of the end of thecircuit board 40A as shown in FIG. 3B. The flexible cable 41 connectedto the end of the circuit board 40A is connected to the circuit board40G on which the imaging device 11G and the CDS circuit 13G are mounted.Such arrangement allows signals output from the CDS circuits 13R, 13G,13B to be transmitted to the A/D converters 15R, 15G, 15B through shortpaths, respectively.

Subsequently, referring to FIGS. 4A and 4B, an exemplified arrangementof each of the circuit boards 40A, 40B, 40G, 40R will be described. FIG.4A illustrates that the respective circuit boards 40A, 40B, 40G, 40Rfixed to the color separation prism 30 as shown in FIGS. 2 and 3 arelaid out and arranged on the same plane. The arrangement of therespective circuit boards 40 shown in FIG. 4A corresponds to thearrangement of the respective circuit boards 40 before being laid out asshown in FIG. 4B. The state shown in FIG. 4A can be attained bystretching each circuit board 40 in the direction indicated by the arrowA1 in FIG. 4B. As shown in FIG. 4B, the color separation prism 30, theconductive plate 90, and so on are not illustrated in the figure for theconvenience of explanation.

As shown in FIG. 4A, the circuit board 40R mounting the imaging device11R, the circuit board 40G mounting the imaging device 11G, and thecircuit board 40B mounting the imaging device 11B are connected to oneanother through the flexible cable 41, respectively. The circuit boards40R, 40G, 40B are aligned with the circuit board 40G in the centerthereof. In addition, the circuit board 40A is connected to the circuitboard 40G arranged in the center through the flexible cable 41. Thecircuit board 40A is connected to the circuit board 40G such that it canbe arranged substantially at a right angle with the aligned circuitboards 40R, 40G, 40B. In other words, the aligned circuit boards 40R,40G, 40B form a T-shape with the circuit board 40A.

The CDS circuits 13R, 13G, 13B are arranged on the surfaces of therespective circuit boards 40R, 40G, 40B on the other sides where theimaging devices 11R, 11G, 11B are not arranged. Signals output from theCDS circuits 13R and 13B are transmitted to the A/D converters 15R, 15G,15B on the circuit board 40A after passing through the circuit board 40Glocated in the center of the circuit arrangement.

The circuit boards 40B and 40R have a defined side length as indicatedby the arrow A2 as shown in FIGS. 4A and 4B. This length corresponds tothe height of the output surface of the color separation prism 30 (seeFIG. 3) from which color-separated light is output, so that it can beseverely limited in design. In contrast, the circuit board 40G has aside length indicated by the arrow A3 as shown in FIG. 4A which is notseverely limited in design. Thus, the area of the circuit board 40G maybe larger than that of the other circuit boards. Hence, the circuitboard 40G is configured to once correct signals from the circuit boards40R and 40B and then transmit the signals to the circuit board 40A.Thus, the dimensions of the circuit board A can also be designed to besmall.

As shown in FIG. 5A, it should be noted that the circuit board 40A withthe mounted A/D converters 15R, 15G, 15B may be connected to the circuitboard at the end (40R in FIG. 5A) among the circuit boards 40R, 40G, 40Baligned. When these circuit boards are arranged in such L-shape, thelengths of the transmission path from the circuit board 40A to thealigned respective circuit boards 40B, 40G, 40R may vary. As shown inFIG. 5A, the distance between the circuit board 40B and the circuitboard 40A is long, while the distance between the circuit board 40R andthe circuit board 40A is short. Therefore, the phase characteristics andthe frequency characteristics of signals transmitted from the respectivecircuit boards 40B, 40G, 40R may vary, which is unfavorable.

Furthermore, when the respective circuit boards 40A, 40B, 40G, 40R asillustrated in FIG. 5A are assembled, it is difficult to bend a flexiblecable 41′ connecting the circuit board 40R and the circuit board 40A.The circuit boards 40R and 40A may have increased stress, resulting inmisalignment thereof.

Furthermore, as shown in FIG. 5B, when the circuit boards 40R, 40G, 40Bare respectively connected to the circuit board 40A through flexiblecables 41″, the circuit boards 40R, 40G, 40B may not share the supplyfrom a common power source. In other words, the circuit boards 40R, 40G,40B may independently receive power from the circuit board 40A, so thatthe width of each flexible cable 41″ may be large. Accordingly, a largearea may be necessary for the circuit board 40A. Furthermore, similar tothe case shown in FIG. 5A, the flexible cables 41″ are difficult tobend, so that the respective circuit boards 40A, 40B, 40G, 40R may beaffected by increasing stress.

In other words, according to the embodiment of the invention, powersupplied from the circuit board 40A is temporally supplied to thecircuit board 40G and then distributed to the circuit board 40R and thecircuit board 40B. Therefore, the width of the flexible cable 41connecting the circuit board 40G and the circuit board 40A may be short.As a result, the area of the circuit board 40A can be reduced.

Furthermore, according to the embodiment of the invention, therespective circuit boards 40A, 40B, 40G, 40R may be arranged as shown inFIG. 4A to shorten the transmission distance from the CDS circuits 13R,13G, 13B to the A/D converter 15R, 15G, 15B. Therefore, the phasecharacteristics and frequency characteristics of analog video signalscan be prevented from deteriorating.

Furthermore, according to the embodiment of the invention, the A/Dconverters 15R, 15G, 15B, the second control unit 18, the timinggenerator 19, and so on are arranged on the circuit board 40A having nolimitation to the height of the surface of the color separation prism 30from which color-separated light is output. Therefore, the entireimaging apparatus 100 can be small-sized.

Furthermore, according to the embodiment of the invention, a groundlayer is arranged on the rear side of the surface on which an analogtransmission circuit is mounted to further prevent analog video signalsfrom receiving noise. FIG. 6 is an exploded view showing each layer ofthe circuit boards 40A, 40B, 40G, 40R and the flexible cable 41 whilethe respective circuit boards are laid out as shown in FIG. 4A.

According to the embodiment, the flexible cable 41 is formed of a singleplate including two layers, that is, a ground layer 41 a and a signallayer 41 b. Each of these layers, the ground layer 41 a and the signallayer 41 b, is connected to the circuit boards 40R, 40G, 40B. Thecircuit boards 40R, 40G, 40B arranged on the ground layer 41 a are madeof two layers: signal layers 40Ra and 40Rb, signal layers 40Ga and 40Gb,and signal layers 40Ba and 40Bb, respectively. The circuit boards 40R,40G, 40B arranged on the signal layer 41 b are made of two layers:signal layers 40Rc and 40Rd, signal layers 40Gc and 40Gd, and signallayers 40Bc and 40Bd, respectively.

According to the embodiment, circuits for analog-signal transmission,such as the imaging devices 11R, 11G, 11B and the AD converters 15R,15G, 15B, are arranged on the ground layer 41 a of the flexible cable41. In addition, the CDS circuits 13R, 13G, 13B and the power-decouplingcapacitor 60 are arranged on the signal layer 41 b of the flexible cable41.

According to the above-described configuration, the ground layer 41 ashields the analog-signal transmission circuits. Thus, noise can beprevented from coupling with analog video signals. Also, the frequencycharacteristics and the phase characteristics of analog video signalscan be prevented from deteriorating.

Furthermore, the respective circuits are mounted on the both sides ofthe flexible cable 41 in the arrangement as illustrated in FIG. 6. Thus,in the assembled state as shown in FIG. 4B, digital circuits, such asthe second control unit 18 and the timing generators 19, are arranged onthe surface rear to the side where the imaging devices 11R, 11G, 11B arearranged on the circuit boards 40R, 40G, 40B, respectively. Therefore,the possibility of noise from the digital circuits to the imagingdevices 11R, 11G, 11B becomes low, so that signals output from therespective imaging devices 11R, 11G, 11B may have favorablecharacteristics with less influence of noise.

Furthermore, according to the above-described embodiment, the CDScircuits 13R, 13G, 13B are mounted on the surfaces opposite to those onwhich the imaging devices 11R, 11G, 11B are mounted respectively.Alternatively, the CDS circuits may be arranged on the same surface onwhich the respective imaging devices 11R, 11G, 11B are arranged.

Furthermore, the above-described embodiment of the invention has beenapplied to the imaging apparatus provided with three imaging devices.However, an applicable apparatus is not limited to such imagingapparatus. An embodiment of the invention can be applied to any of otherapparatuses in the case where the apparatus includes a plurality ofsensor devices and intends to decrease the deterioration of the phaseand frequency characteristics of signals transmitted between circuits.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An imaging block comprising; a prism configured to separate lightincident through a lens into at least two colors and output the light; afirst imaging device and a second imaging device each configured togenerate a video signal by photoelectrically converting the separatedlight output from the prism; an analog/digital converter configured toconvert the video signal output from each of the first imaging deviceand the second imaging device into a digital signal; a timing generatorconfigured to generate video-signal processing clock for driving thefirst imaging device, the second imaging device, and the analog/digitalconverter; a first circuit board on which the first imaging device ismounted; a second circuit board on which the analog/digital converterand the timing generator are mounted; and a third circuit board, onwhich the second imaging device is mounted, connected to both the firstcircuit board and the second circuit board through a cable, wherein thefirst imaging device mounted on the first circuit board and the secondimaging device mounted on the third circuit board are fixed to outputsurfaces of the prism, wherein the second circuit board is arranged sothat a surface of the second circuit board is substantiallyperpendicular to a surface of the first circuit board and a surface ofthe third circuit board, and wherein the analog/digital converter andthe timing generator are mounted on another surface of the secondcircuit board opposite to the surface of the second circuit board on theside where the first circuit board and the third circuit board arearranged.
 2. An imaging block according to claim 1, wherein the firstcircuit board is connected to the second circuit board substantially ata right angle, with the third circuit board at the center, in a state inwhich the first circuit board, the second circuit board and the thirdcircuit board are laid out.
 3. An imaging block according to claim 2,wherein the length of the third circuit board in a widthwise directionis longer than the length of the first circuit board in the widthwisedirection.
 4. An imaging block according to claim 2, wherein theanalog/digital converter is arranged at the end of the second circuitboard on the side thereof wired with the cable for connecting to thethird circuit board.
 5. An imaging block according to claim 2, whereinthe cable is a flexible cable including two layers of a ground layer anda signal layer, and wherein the first circuit board, the second circuitboard, and the third circuit board are arranged on a surface of both theground layer and the signal layer.
 6. An imaging block according toclaim 5, wherein the analog/digital converter and the timing generatormounted on the second circuit board are arranged on the side of theground layer of the flexible cable.
 7. An imaging block according toclaim 6, wherein a power decoupling circuit is arranged on the secondcircuit board arranged on the side of the signal layer of the flexiblecable.
 8. An imaging apparatus comprising: a prism configured toseparate light incident through a lens into at least two colors andoutput the light; a first imaging device and a second imaging deviceeach configured to generate a video signal by photoelectricallyconverting the separated light output from the prism; an analog/digitalconverter configured to convert the video signal output from each of thefirst imaging device and the second imaging device into a digitalsignal; a timing generator configured to generate a video-signalprocessing clock for driving the first imaging device, the secondimaging device, and the analog/digital converter; a first circuit boardon which the first imaging device is mounted; a second circuit board onwhich the analog/digital converter and the timing generator are mounted;and a third circuit board, on which the second imaging device ismounted, connected to both the first circuit board and the secondcircuit board through a cable, wherein the first imaging device mountedon the first circuit board and the second imaging device mounted on thethird circuit board are fixed to output surfaces of the prism, whereinthe second circuit board is arranged so that a surface of the secondcircuit board is substantially perpendicular to a surface of the firstcircuit board and a surface of the third circuit board, and wherein theanalog/digital converter and the timing generator are mounted on anothersurface of the second circuit board opposite to the surface of thesecond circuit board on the side where the first circuit board and thethird circuit board are arranged.